| 摘要 |
To move a door, e.g. up-and-over garage door 28, a carriage 18 is slid in a profile rail 10 when geared, d.c. electric motor 20 rotates pinion 24 which engages tensional chain 12 fixed in the rail. Alternatively, the carriage may roll in the rail, and the chain may be replaced by a rack or a screwthread. The rail may be of extruded aluminium. The carriage has brushes to contact conductors on the rail, and carries a magnet to actuate microswitches. <IMAGE> |
